1. Field of the Invention
The present invention relates to an apparatus and method for automatically detecting and reading graphic matter and more particularly to the detection of documents on a flat bed scanner.
2. Description of the Related Art
Recent developments in the use of high speed, low cost digital electronic imaging systems to process, transmit and display digital information have substantially increased the demand for optical scanners to convert graphic matter, such as text and pictures, into a digital electronic form. A variety of optical scanners, including facsimile machines and digital copiers, have been developed to meet this growing demand. Typically, optical scanners fall within two categories, reflective scanners for opaque objects, such as documents and photographs, and transmissive scanners for transparent objects, such as slides and transparencies.
Reflective scanners are used with opaque objects and project light onto the side of the object to be scanned. When illuminated by the reflected light, the object is viewable by a digital camera which in turn converts the image into a digital electronic form. The conventional reflective scanner operates by moving the digital camera row by row relative to the object to be scanned.
In one conventional embodiment, the relative movement of the digital camera with respect to the object may be achieved using a document feeder to draw the object, such as a document, across the field of view of the digital camera. The document feeder often comes with a paper tray to enable the scanner to draw several pages, one at a time, across the scanner. While suitable for many general applications, the scanner with a document feeder cannot accommodate odd-sized or bound materials. In addition, the document feeder can jam the paper or draw-in the paper at an angle causing the document to misalign with the digital camera. Alignment problems of this type occur most often when the document has an unusual thickness or paper size. Unusual documents when misread by the scanner can result in poor image quality when viewed electronically. Typically, such scanners are used in applications where the volume of materials scanned outweigh considerations for image quality. However, a skewed image is undesirable in desk top publishing applications where the quality of the image is desired over volume.
For applications where quality of the image is desired, an optical scanner of the type known as a flat bed scanner is used. Such scanners typically use a transparent platen to support the image to be scanned. The image is placed by the operator on the platen. Once positioned on the platen, the document remains stationary relative to the platen. In this type of scanner, the digital camera and a reflective light source move relative to the platen. This type of relative movement can be achieved conventionally by moving the platen and document across a stationary digital camera and light source. Alternatively, this type of relative movement can be achieved by moving the digital camera and light source along rails within the base housing relative to the platen and document. Regardless of which method of relative movement is used, the light source projects light upon the portion of the object within the field of view of the camera. As documents and photographs are moved relative to the scanning camera, the light source and camera cooperate to incrementally scan across an image line by line. While suitable for high quality image processing, the flat bed scanner is not well suited for processing several pages of documents at a time. This problem is due in part to the need for manual adjustment of each image on the platen. The problem is compounded by the software and scanner which must then be manually continued by the operator to begin scanning the image. Such manual configuration may include configuring the scanner to recognize the dimensions of the paper and manually signaling the scanner that an image has been placed on the platen.